As one way for achieving higher integration of a semiconductor device, there is a technique in which wirings are formed in a multi-layered manner. In order to adopt a multi-layered wiring structure, an n-th wiring layer and an (n+1)-th wiring layer are connected via a conductive layer, and a thin film called an interlayer insulation film is formed at an area except for the conductive layer. As a typical example of the interlayer insulation film, there is known an SiO2 film. However, recently, in order to achieve much higher speed for operation of a device, it has been required to further decrease the dielectric constant of the interlayer insulation film.
In view of such requirement, a fluoridation carbon film that is a chemical compound of carbon (C) and fluorine (F) has been paid attention to. While a dielectric constant of the SiO2 film is around 4, a dielectric constant of the fluoridation carbon film can be not higher than 2 if a kind of source gas is suitably selected. Thus, the fluoridation carbon film is a much effective film as an interlayer insulation film. Various gases are known as a source gas for the fluoridation carbon film (Japanese Patent Laid-Open Publication No. 144675/1998: section 0017). For example, a C5F8 (octafluorocyclopentene) gas is a superior source gas because it can form a film having a network structure.
In addition, as a conventional art relating to the source gas for the fluoridation carbon, there is known a technique disclosed in Japanese Patent Laid-Open Publication No. 237783/1997. According to the technique, hexafluoro-1,3-butadiene or hexafluoro-2-butyne is used as a source gas, and an insulation film consisting of a fluorinated amorphous carbon is formed by means of a plasma CVD method, so that a dielectric constant of 2.1 or 2.5 can be respectively obtained.
According to Japanese Patent Laid-Open Publication No. 220668/2002, various unsaturated carbon fluorides are used as a film-forming gas, and film density and film surface roughness are studied.
According to Japanese Patent Laid-Open Publication No. 332001/2000, by means of a plasma CVD method using a high-purity octafluorocyclopentene, a film having a dielectric constant of 2.4 can be obtained.